IR spectroscopy measurements may be useful for a variety of purposes including aerospace, automotive and industrial applications, as well as biological and bio-medical applications. For example, infrared (IR) radiation is readily absorbed or reflected by materials. As such, IR spectroscopy measurements may indicate a condition of a wide variety of organic as well as inorganic materials.
For example, resin-fiber composite material used in aircraft parts may degrade over time due to a variety of reasons including heat or ultraviolet (UV) light exposure, which may cause chemical degradation to a polymer structure to occur, thereby affecting the desired properties of the polymer structure including structural integrity such as strength of the composite material. In addition, resin-fiber composite material may be subjected to other sources of effect such as high intensity electrical discharges near or on the composite material such as caused by lightening strikes.
Polymer composite materials, such as resin-fiber composite materials may include embedded metal such as what is known in the art as interwoven wire fabric (IWWF) or expanded aluminum foil (EAF), which includes metal wire interwoven into the polymer composite material, which provides a degree of protection against lightening strikes near or on the material, by providing a low resistance path to diffuse the energy over a wider area.
High intensity electrical discharges, such as lightening strikes to a composite material including IWWF may result in the non-compliant properties of the IWWF within the composite material, resulting in a portion of the composite material that is non-compliant, including beyond the area of the material that is visibly struck by lightening. The missing IWWF must be replaced to provide electromagnetic event (EME) protection for the aircraft, including removing areas with IWWF loss and replacing the removed areas with good IWWF.
One non-destructive method in the prior art of ascertaining the condition of polymer composite material, such as the degree of UV or heat effect to composite materials, includes IR spectroscopy of the polymer composite material, and is outlined in U.S. Pat. No. 7,113,869, which is hereby incorporated by reference in its entirety.
Other non-destructive methods in the prior art include using IR spectroscopy to determine the amount of a chromated conversion coating on a metallic substrate (U.S. Pat. No. 6,794,631), determining the amount of an anodized coating on a metallic substrate, (U.S. Pat. No. 6,784,431), determining an amount of opaque coating on a substrate (U.S. Pat. No. 6,903,339), and determining an amount of heat exposure effect to a resin-fiber composite substrate (U.S. Pat. No. 7,115,869), all of which are fully incorporated herein by reference.
None of the above methods and associated devices, however, disclose a method that is suitable for performing IR spectroscopy to detect the presence or absence of embedded (integral) metallic material in a polymer composite material, and to thereby determine a degree of effect to the polymer composite material, particularly in a field environment, such as in aircraft maintenance.
Thus, there is a continuing need for improved IR non-destructive testing methods including a method that is suitable for performing IR spectroscopy to detect the presence or absence of embedded (integral) metallic material in a polymer composite material, and to thereby determine a degree of effect to the polymer composite material, particularly in a field environment, such as in an aircraft maintenance process.
Therefore it is an object of the invention to provide a method that is suitable for performing IR spectroscopy to detect the presence or absence of embedded (integral) metallic material in a polymer composite material, and to thereby determine a degree of effect to the polymer composite material, particularly in a field environment, such as in an aircraft maintenance process.